(a) Field of the Invention
The present invention relates to a method for synchronization of a D2D terminal with another D2D terminal in a D2D communication network.
(b) Description of the Related Art
In a long term evolution (LTE) mobile communication system, research for supporting device to device (D2D) communication is in progress. In the D2D communication, a terminal may directly transmit and receive data to and from a contiguous terminal without passing through a base station. In LTE D2D which is discussed in a 3GPP standard commission, a method is discussed in which a D2D terminal provides synchronization in order to support the D2D communication, and some of D2D terminals may operate as a D2D synchronization source according to a determined agreement. The D2D synchronization source transmits a D2D synchronization signal (D2DSS) for matching synchronization and a physical D2D synchronization channel (PD2DSCH) for transferring additional information for the synchronization to provide a synchronization timing reference to a contiguous D2D terminal. The D2D terminal that receives the D2D synchronization signal and the D2D synchronization channel from a contiguous D2D synchronization source configures the synchronization timing reference based on information included in the received D2D synchronization signal and D2D synchronization channel.
A method for the terminal supporting the D2D communication to match the synchronization with the contiguous D2D terminal may vary depending on whether the D2D terminal is controlled by the base station. When the D2D terminal is directly controlled from the base station, the D2D terminal may receive a downlink synchronization timing reference of the base station through synchronization signals (e.g., a primary synchronization signal and a secondary synchronization signal) transmitted by the base station. Further, in order to provide synchronization timing to the contiguous D2D terminal, the base station commands a specific D2D terminal to operate as the D2D synchronization source.